Scenario 1 is a badbeat. I don't see how putting all your chips in earlier would have changed anything. Honestly, TPTK is not a monster, it's just a pair. Don't put your chips in on such a week hand unless you think you know you're ahead. Besides,you're playing microlimits and people are idiots. He could have as likely had two pair.

If bad beats are driving you nuts, remember this: good players play in hands because they know/believe they are ahead. Therefore, most of the time they lose hands is because of bad beats. It's just a regular thing as you progress.

I think the other scenarios are well discusses. You knew you were beat with the QQAA board. Playing when you know you're beat is like shooting yourself in the foot.